You are absolutely right; you do not want to get very, very dark by glazing. Have a look at candles painted (possibly by Uschi? I can't remember) in this forum (probably w/c Gallery?). This will convince you that w/c absolutely can produce this sort of painting.
What you want to do is mix
a very dark color, and brush it on in one application (if possible). Then, in some areas, soften the edge. Judging from this photo, you might want some slightly less black areas, so a tiny bit more water in your first mixed black will work. See if there was a WIP on those candle pictures; that would probably be perfect advice.
Note: I see you're a bit new to WC! so I figure I should explain: Have you seen the search facility for a particular forum? Just click on the Gallery subforum, then just above the list of all the threads, on the right side, there's a search box for looking through that particular forum.
P.S. Forgot to say -- lovely photograph! Great!
P.P.S. I found one link, to give you a taste. This is by Uschi, and there are more than one of them, and you can find them by using the 'Forum' search (click it and it opens a search box):